SIDE_A_MISSED_COOPERATIVE_AIRCRAFT
Viewing this guide for
Applicable alarms (1)
SIDE_A_MISSED_COOPERATIVE_AIRCRAFT
Likely outcomes — click to expand
Based on 74 missions where this alarm fired in the last 90 days as of 2026-10-13
Grounding vs discrepancy (of 2 ZERP issues filed on these missions)
Frequently co-occurring alarms (% of the 74 missions above)
Aggregated from fleet operations and refreshed daily. Individual outcomes may vary by site and configuration.
Background
Section titled “Background”This is a DAA related detection performance alarm. The DAA Tracker uses the detections from the ADSB device in each compute. This alarm gets activated when the ADSB device in compute A does not get position detections that compute B sees during a minute of flight (or data streaming when docked) inside of the safety puck 5 km radius laterally and 2.5 km half height. This indicates degradation in either the device or the antennas. Compute A is considered the main source of detections.
During preflight it will block launch; during flight it will command a DockAsap so the cooperative DAA system avoids working with degraded hardware.
Troubleshooting Steps
Section titled “Troubleshooting Steps”graph TD
does-this-alarm-occur-during-preflight{"<small><b>Step 1</b></small><br/>Question: Does this alarm occur during prefligh..."}
wait-for-2-minutes-or-until-the-alarm-c["<small><b>Step 2</b></small><br/>Action: Wait for 2 minutes or until the alarm..."]
has-the-alarm-cleared{"<small><b>Step 3</b></small><br/>Question: Has the alarm cleared?"}
the-aircraft-may-return-to-service("<small><b>Step 4</b></small><br/>Reference: The Aircraft may return to service.")
check-the-alarm-report-is-the-missed-ai{"<small><b>Step 5</b></small><br/>Question: Check the alarm report. Is the missed..."}
wait-until-the-aircraft-has-left-the-vic["<small><b>Step 6</b></small><br/>Action: Wait until the Aircraft has left the ..."]
wait-for-two-2-minutes["<small><b>Step 7</b></small><br/>Action: Wait for two 2 minutes."]
has-the-alarm-cleared-2{"<small><b>Step 8</b></small><br/>Question: Has the alarm cleared?"}
the-aircraft-may-return-to-service-2("<small><b>Step 9</b></small><br/>Reference: The Aircraft may return to service.")
power-cycle-the-aircraft-see-power-cycle{"<small><b>Step 10</b></small><br/>Question: Power cycle the Aircraft. See Power ..."}
the-aircraft-may-return-to-service-3("<small><b>Step 11</b></small><br/>Reference: The Aircraft may return to service.")
escalate-to-daa-tracker-on-call{{"<small><b>Step 12</b></small><br/>Escalation: Escalate to P2 Zip DAA Tracker On Call."}}
did-alarm-clear-during-the-return-fligh{"<small><b>Step 13</b></small><br/>Question: Did alarm clear during the return fli..."}
continue-to-the-next-step-flight-yes["<small><b>Step 14</b></small><br/>Action: Continue to the next step."]
power-cycle-the-aircraft-see-power-cycle-2["<small><b>Step 15</b></small><br/>Action: Power cycle the Aircraft. See Power ..."]
did-the-alarm-clear-flight-no{"<small><b>Step 16</b></small><br/>Question: Did the alarm clear?"}
continue-to-the-next-step-flight-no-yes["<small><b>Step 17</b></small><br/>Action: Continue to the next step."]
escalate-to-daa-tracker-on-call-2{{"<small><b>Step 18</b></small><br/>Escalation: Escalate to P2 Zip DAA Tracker On Call."}}
is-this-the-first-occurrence-of-the-ala{"<small><b>Step 19</b></small><br/>Question: Is this the first occurrence of the a..."}
in-the-alarm-report-is-sum-total-detecti{"<small><b>Step 20</b></small><br/>Question: In the alarm report Aircraft/Droid ..."}
sum-total-detections-compute-a-equals-ze["<small><b>Step 21</b></small><br/>Action: **sum_total_detections_compute_a ==..."]
sum-total-detections-compute-a-greater-t["<small><b>Step 22</b></small><br/>Action: **sum_total_detections_compute_a ..."]
not-first-occurrence-commercial-operatio["<small><b>Step 23</b></small><br/>Action: **Commercial Operations**: Contact p2..."]
was-a-sign-off-to-resume-operations-give{"<small><b>Step 24</b></small><br/>Question: Was a sign-off to resume operations g..."}
resume-operation-the-aircraft-can-return["<small><b>Step 25</b></small><br/>Action: **Resume operation**: The Aircraft ca..."]
replace-compute-board-the-aircraft-may-r["<small><b>Step 26</b></small><br/>Action: **Replace compute board**: Replace th..."]
does-this-alarm-occur-during-preflight -->|Preflight| wait-for-2-minutes-or-until-the-alarm-c
does-this-alarm-occur-during-preflight -->|Flight| did-alarm-clear-during-the-return-fligh
wait-for-2-minutes-or-until-the-alarm-c --> has-the-alarm-cleared
has-the-alarm-cleared -->|Yes| the-aircraft-may-return-to-service
has-the-alarm-cleared -->|No| check-the-alarm-report-is-the-missed-ai
check-the-alarm-report-is-the-missed-ai -->|Yes| wait-until-the-aircraft-has-left-the-vic
check-the-alarm-report-is-the-missed-ai -->|No| wait-for-two-2-minutes
wait-until-the-aircraft-has-left-the-vic --> wait-for-two-2-minutes
wait-for-two-2-minutes --> has-the-alarm-cleared-2
has-the-alarm-cleared-2 -->|Yes| the-aircraft-may-return-to-service-2
has-the-alarm-cleared-2 -->|No| power-cycle-the-aircraft-see-power-cycle
power-cycle-the-aircraft-see-power-cycle -->|Yes| the-aircraft-may-return-to-service-3
power-cycle-the-aircraft-see-power-cycle -->|No| escalate-to-daa-tracker-on-call
did-alarm-clear-during-the-return-fligh -->|Yes| continue-to-the-next-step-flight-yes
did-alarm-clear-during-the-return-fligh -->|No| power-cycle-the-aircraft-see-power-cycle-2
continue-to-the-next-step-flight-yes --> is-this-the-first-occurrence-of-the-ala
power-cycle-the-aircraft-see-power-cycle-2 --> did-the-alarm-clear-flight-no
did-the-alarm-clear-flight-no -->|Yes| continue-to-the-next-step-flight-no-yes
did-the-alarm-clear-flight-no -->|No| escalate-to-daa-tracker-on-call-2
continue-to-the-next-step-flight-no-yes --> is-this-the-first-occurrence-of-the-ala
is-this-the-first-occurrence-of-the-ala -->|Yes| in-the-alarm-report-is-sum-total-detecti
is-this-the-first-occurrence-of-the-ala -->|No| not-first-occurrence-commercial-operatio
in-the-alarm-report-is-sum-total-detecti -->|sum_total_detections_compu...| sum-total-detections-compute-a-equals-ze
in-the-alarm-report-is-sum-total-detecti -->|sum_total_detections_compu...| sum-total-detections-compute-a-greater-t
not-first-occurrence-commercial-operatio --> was-a-sign-off-to-resume-operations-give
was-a-sign-off-to-resume-operations-give -->|Resume operation| resume-operation-the-aircraft-can-return
was-a-sign-off-to-resume-operations-give -->|Replace compute board| replace-compute-board-the-aircraft-may-r
style does-this-alarm-occur-during-preflight fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style wait-for-2-minutes-or-until-the-alarm-c fill:#dcfce7,stroke:#22c55e,color:#14532d
style has-the-alarm-cleared fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style the-aircraft-may-return-to-service fill:#f3e8ff,stroke:#a855f7,color:#581c87
style check-the-alarm-report-is-the-missed-ai fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style wait-until-the-aircraft-has-left-the-vic fill:#dcfce7,stroke:#22c55e,color:#14532d
style wait-for-two-2-minutes fill:#dcfce7,stroke:#22c55e,color:#14532d
style has-the-alarm-cleared-2 fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style the-aircraft-may-return-to-service-2 fill:#f3e8ff,stroke:#a855f7,color:#581c87
style power-cycle-the-aircraft-see-power-cycle fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style the-aircraft-may-return-to-service-3 fill:#f3e8ff,stroke:#a855f7,color:#581c87
style escalate-to-daa-tracker-on-call fill:#fef3c7,stroke:#f59e0b,color:#78350f
style did-alarm-clear-during-the-return-fligh fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style continue-to-the-next-step-flight-yes fill:#dcfce7,stroke:#22c55e,color:#14532d
style power-cycle-the-aircraft-see-power-cycle-2 fill:#dcfce7,stroke:#22c55e,color:#14532d
style did-the-alarm-clear-flight-no fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style continue-to-the-next-step-flight-no-yes fill:#dcfce7,stroke:#22c55e,color:#14532d
style escalate-to-daa-tracker-on-call-2 fill:#fef3c7,stroke:#f59e0b,color:#78350f
style is-this-the-first-occurrence-of-the-ala fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style in-the-alarm-report-is-sum-total-detecti fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style sum-total-detections-compute-a-equals-ze fill:#dcfce7,stroke:#22c55e,color:#14532d
style sum-total-detections-compute-a-greater-t fill:#dcfce7,stroke:#22c55e,color:#14532d
style not-first-occurrence-commercial-operatio fill:#dcfce7,stroke:#22c55e,color:#14532d
style was-a-sign-off-to-resume-operations-give fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style resume-operation-the-aircraft-can-return fill:#dcfce7,stroke:#22c55e,color:#14532d
style replace-compute-board-the-aircraft-may-r fill:#dcfce7,stroke:#22c55e,color:#14532d Hover or focus a block to preview it. Select the block to keep the preview open.
1 question
Does this alarm occur during preflight or flight?
2 action
Wait for 2 minutes or until the alarm clears.
3 question
Has the alarm cleared?
4 reference
The Aircraft may return to service.
5 question
Check the alarm report. Is the missed Aircraft ICAO (transform it from integer to hex) still in the vicinity in the Fleet View?
6 action
Wait until the Aircraft has left the vicinity and then continue with the next step.
7 action
Wait for two (2) minutes.
8 question
Has the alarm cleared?
9 reference
The Aircraft may return to service.
10 question
Power cycle the Aircraft. See Power Cycle Aircraft. Has the alarm cleared?
11 reference
The Aircraft may return to service.
12 escalation
Escalate to P2 Zip DAA Tracker On Call.
13 question
Did alarm clear during the return flight?
14 action
Continue to the next step.
15 action
Power cycle the Aircraft. See Power Cycle Aircraft.
16 question
Did the alarm clear?
17 action
Continue to the next step.
18 escalation
Escalate to P2 Zip DAA Tracker On Call.
19 question
Is this the first occurrence of the alarm for this Aircraft in the past 24 hours?
20 question
In the alarm report (Aircraft/Droid Alarm Report), is
sum_total_detections_compute_a set to “==0” or “>0?” 21 action
sum_total_detections_compute_a == 0- Commercial Operations: The Aircraft can return to service. The alarm is likely to reoccur in subsequent flights.
- Test Operations not relying on ADS-B DAA: The Aircraft may return to service. DAA is not assumed to add safety.
22 action
sum_total_detections_compute_a > 0:- Commercial Operations: The Aircraft may return to service. Note a possible reduction in safety.
- Test Operations not relying on ADS-B DAA: The Aircraft may return to service. DAA is not assumed to add safety.
23 action
Commercial Operations:
Contact p2-avionics-on-call and ask them to run the diagnostic script to determine whether this is a compute fault or degraded aircraft performance.
Test Operations not relying on ADS-B DAA: The Aircraft may return to service. DAA is not assumed to add safety.
Contact p2-avionics-on-call and ask them to run the diagnostic script to determine whether this is a compute fault or degraded aircraft performance.
Test Operations not relying on ADS-B DAA: The Aircraft may return to service. DAA is not assumed to add safety.
24 question
Was a sign-off to resume operations given, or was the instruction to change the compute assembly?
25 action
Resume operation: The Aircraft can return to service.
26 action
Replace compute board: Replace the compute board and then the Aircraft may return to service.
- UMM: Remove Flight Compute Assembly
- UMM: Install Flight Compute Assembly
- UMM: Remove Flight Compute Assembly
- UMM: Install Flight Compute Assembly
Resolution note
This plaintext block is ready to paste into the Resolution Note field on the ZERP issue you're working. The permalink below gives engineering review access to the full step-by-step timeline including any back-navigation; share it if the case needs a deeper look.
Permalink:
Session is too large to fit in a URL. Use Download session JSON to share the timeline out-of-band.
Did this guide help you get unblocked?
Open suggestions
There are no open suggestions.